This invention relates generally to an aircraft engine exhaust nozzle system, and, more particularly to an aerodynamically-shaped deformable plug centrally located in the path of the engine exhaust gases, the plug having forward and rear fairings actuated by a simplified actuation system.
Jet engines are usually made up of a tubular housing or duct and contains therein an intake orifice, a combustion chamber, and an exhaust nozzle aft of the combustion chamber having a restricted orifice commonly known as the throat.
It has been found that varying the exhaust nozzle throat area enables an engine to maintain the design airflow with an increased fuel flow thereby increasing the engine thrust range. Likewise varying the inlet orifice area produces a more flexible control of the airflow so that it may be adjusted to variable flight conditions. A jet engine having these orifices variable, then, has the advantages of increased thrust range, increased upper altitude limit of operation, and more efficient variable Mach number flight.
It is also highly desirable to be able to control effective thrust in flight. This is particularly so in the case of tactical military airplanes, which may be required to decelerate rapidly in combat maneuvers or limit their speed in steep dives in bombing operations. Conventionally, speed brakes are used for this purpose.
Various types of thrust reversers have been in use for many years primarily to reduce landing run, although some have been successfully used in flight to reduce forward speed more rapidly than by throttling the engine. All of them utilize a basic principle of blocking the rearward flow of the exhaust gas stream and diverting it laterally. If the stream has no forward component it will act in the manner of a speed brake by interference with the free airstream. Normally, however, the stream is directed substantially forwardly to produce an actual reverse thrust. One common type uses a pair of deflectors which meet externally behind the nozzle to divert the stream laterally in opposite directions, usually with a forward component. Another similar type has doors mounted within the nozzle to block flow, lateral openings in the nozzle, and doors or reflectors which normally cover these openings, but may be swung outward to uncover the openings and direct the diverted streams laterally and forwardly. In another type, doors within the nozzle may be moved to block flow, and cascade passages are uncovered in the sidewalls to allow the gas to issue laterally and forwardly. Such a related device has been described in U.S. Pat. NO. 3,774,868.
The major problem associated with the devices of the past for varying the thrust capabilities of a jet engine has been the highly complex nature of the mechanisms involved in the actuation of the device, and, as a result thereof the unreliable operation of the overall system.